Davenport. — Urnatella gracilis. 



PLATE II. 



ABBREVIATIONS. 



gn. 



in. 



7ns' d nil. 



mn. 



nl. 



nph. 



ce. 



of. air. 



patchy. 



rt. 



vt. or 



vt. gran. 



Ganglion. 



Intestine. 



Mesoderm. 



Muscle fibre. 



Nucleus. 



Nepliridium. 



Oesophagus. 



Atrial opening. 



Parenchyme. 



Rectum. 



Yolk granules. 



Fig. 8. 



10. 



11. 

 12. 



13. 

 14. 

 15. 

 16. 

 17. 



Longitudinal section through proximal part of stalk of Urnatella. Third 

 stage in the formation of yolk granules. X 610. 



Cross section through distal segment of stalk, showing ectoderm and pa- 

 renchymatous tissue inside. X 405. 



Third stage in the development of the stalk muscles. Zeiss, j-\ oilimmers., 

 Oc. 2. X 1350. 



Second stage in the development of the stalk muscles. X 1350. 



Termination of excretory tubule of stalk in flame cell. The position of 

 the calyx is above. X 305. 



First stage in development of yolk in stalk. X 610. 



Second stage in development of yolk in stalk. X 610. 



Median section through young stalk (age of Fig. 31 in Plate V.). X 165. 



Fourth stage in the development of the stalk musculature. X 1350. 



First stage in the development of the stalk musculature. X 1350. 



